<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>体验Bootstrap</title>
  <link rel="stylesheet" href="./Bootstrap/css/bootstrap.min.css">
  <style>
    .container {
      background-color: pink;
    }
  </style>
</head>
<body>
  <div class="container">
    <div class="row">
      <div class="col-md-3 col-sm-6 col-xm-12">1</div>
      <div class="col-md-3 col-sm-6 col-xm-12">2</div>
      <div class="col-md-3 col-sm-6 col-xm-12">3</div>
      <div class="col-md-3 col-sm-6 col-xm-12">4</div>
    </div>
  </div>
</body>
</html>